i totally understand. I am almost 20, and for the first 19 years of my life i didn't have this problem. I was extremely social, got great grades and was very happy. For about 6 months in every situation I found myself being worried, distracted, not present, even trying to come up with what I would say next before I would say it. I found myself being worried about what people thought of me, but more importantly i didn't know myself. I would even be worried about people I didn't even like, but I knew i didn't like them. I couldn't act on what I felt because I would get distracted with the given situation and would worry about it. I felt like I understood too much and was on a different plain than everyone else. However i know i have so much potential.
I haven't fully corrected the problem however am figuring out myself again. Here are some steps:
-Don't look back: For me I was living in the past, worrying about things that i knew didn't matter but i couldent help it. Everytime I would start to do this I would catch myself and force myself not to do it.
Do not worry about what your going to say:
This was very hard and is still hard for me but under no circumstances worry about what your going to say.
Stop caring about others for a while and focus on yourself:
When I started doing this my problem would seem to vanish. If a situation is not peaking your interest or serving goals that benifit you, just leave it to find something better. Im not saying abide by this in your life, it just helps if you do it for a couple days to get your mind back on track.
Try to look at the bigger picture
The last and best thing that has helped me is to go into the doctor and talk to him. I had been suspecting I had some form of ADD, but was in wonderment because I have never had any of these symptoms before a year ago. I started taking riddalin that I bought from a friend and it helped alot. Then, after more research I found some 30mg adderral and started taking it without seeing a doctor. I saw amazing improvement. I started doing things that felt like me again. I felt more and thought less. however i still wake up in my mind time again and worry about how good i was doing and how to keep it up. However I started getting mad at myself when this happened and would suppress it as fast as possible. Phycyatrists are good, but i had a very severe problem. I saw a medical doctor and got perscribed aderol. Doing much better now, however still have the symptoms time again. Getting a gf really helped as well because when I am around her I feel completely comfortable, even in large groups.
As crazy as it sounds, getting drunk with friends once a week also helped me. good luck man, -jamin